A series of coordination polymers {[Ln(aobtc)(H2O)4]·Hbipy·H2O}n (H4aobtc = azoxybenzene-2,2′,3,3′-tetracarboxylic acid, bipy = 4,4′-bipyridine, and Ln = Sm(1), Eu(2), Gd(3), Tb(4), Dy(5), Er(6)) have been synthesized and characterized systematically. The cationic Hbipy+ guest incorporated polymers are isostructural sets, featuring a one-dimensional (1D) zigzag double chain edifice composed of binuclear clusters [Ln2(H4aobtc)2], with the Hbipy+ guest being located on two sides. These 1D chains are further interlinked into a 2D layer structure, and further extended into a 3D framework through hydrogen bonding interactions. The luminescence emission spectra of polymers 2 and 3 are based on the H4aobtc acid ligands, while 1 and 4 display the characteristic f–f transitions of Ln(III) ions. Magnetic measurements revealed the presence of ferromagnetic behavior in polymer 3. The magnetic behaviors of 4 and 6 are ascribed to the depopulation of the Stark levels and/or weak antiferromagnetic interactions within MOFs at lower temperature. Slow relaxation is observed through the alternating-current susceptibility measurements for 5 at lower temperature, and the coexistence of weak ferromagnetism corresponding to the spin-canting-like behavior.

•Two new lanthanide–organic coordination polymers have been obtained successfully.•They both incorporate hydroxyl bridged tetranuclear clusters.•The polymer 2 shows characteristic f-f transition luminescence of Tb(III) ion.•Polymer 2 can be considered as a fluorescent molecular sensor for zinc cation.•The existence possible antiferromagntic interactions between adjacent Gd(III) ions.Two lanthanide–organic coordination polymers incorporating both substituted imdazole dicarboxylate and benzene monocarboxylate auxiliary ligand, namely, {[Gd2(μ3-OH)(pimda)(imba) (H2pimda) H2O]·2H2O}n (1) and {[Tb2((μ3-OH)(pimda)(imba) (H2pimda) H2O]·2H2O}n (2) (H3pimda = 2-propyl-1H-imidazole-4,5-dicarboxylic acid and H2imba = 4-(1H-imidazole-1-ly) benzoic acid) have been obtained under the hydrothermal conditions, and have been structurally characterized by elemental analysis, IR spectrum and single X-ray diffraction. The polymers are isostructural, both crystallizing in the triclinic system, with space group of p-1. They display one dimensional (1-D) double-stranded ribbon chains based on hydroxyl-bridged [Ln4pimda2] tetranuclear unit as second building block, which are interlinked forming 2-D corrugated layer. The extensive hydrogen bondings further extend these 2-D lamellar networks into 3-D supramolecular architecture. The emission spectrum of polymer 1 exhibits ligand-to-ligand charge-transfer (LLCT) transition luminescence; polymer 2 shows characteristic f-f transition luminescence, which can be considered as a fluorescent molecular sensor for zinc(II) ions in environment. Variable-temperature magnetic susceptibility measurement reveals that multi-bridging fashion of carboxylic group in 1 results in depopulation of the stark levels for a single Gd(III) ion and/or possible antiferromagntic interactions between adjacent Gd(III) cations within the carboxylato bridged binuclear unit.Two new lanthanide–organic coordination polymers incorporating both substituted imdazole dicarboxylate and benzene monocarboxylate auxiliary ligands have been obtained successfully. The polymer 2 shows characteristic f-f transition luminescence, and can be considered as a fluorescent molecular sensor for zinc cation recognition in environment. Variable-temperature magnetic susceptibility measurement reveals that the multi-bridging fashion of carboxylic group in 1 gives rise to possible antiferromagntic interactions between adjacent Gd(III) ions within the carboxylato bridged binuclear unit.Download high-res image (114KB)Download full-size image

A series of five unique d–f heteronuclear luminescent metal–organic frameworks (MOFs) in an entangled polyrotaxane array and the light-harvesting block homonuclear zinc compound have been isolated successfully and characterized. The series of isostructural polymers feature 3,4-connected (4.82)(4.83.92)(6.8.9)2(6.92)(83) topology and high stability, exhibiting diverse void spaces. By taking advantage of the isostructural MOFs 2 and 3, the intensities of red and green emissions can be modulated by adjusting the ratios of EuIII and TbIII ions correspondingly, and white-light emission can be generated by a combination of different doped TbIII and EuIII concentrations. The Tb–Zn-based framework {[Tb3Zn6(bipy2)2(Hmimda)7 (H2O)3]·5H2O}n (3; H3mimda = 2-methyl-1-H-imidazole-4,5-dicarboxylic acid and bipy = 4,4′-bipyridine) can detect trace MgII ion with relatively high sensitivity and selectivity. Dehydrated MOF 3a shows a remarkable emission quenching effect through the introduction of I2 solids. Further investigation indicates that it exhibits turn on/off switchable properties for small solvent molecules or heavy-metal ions. Steady/transient-state near-IR luminescence properties for MOFs 1, 4, and 5 were investigated under visible-light excitation.

•A novel europium coordination complex has been successfully isolated.•It contains mixed carboxylic acid ligands.•It possesses vertical deficient cubane-like array based on tetranuclear {Eu4} cluster.•The complex may be employed as a fluorescent ratiometric probe for pollutant Cd(II) anion.A novel europium complex, formulated as {[Eu4(H3Pimda)4 (Himba)2·4H2O]·4H2O}n (1) (H3Pimda = 2-propyl-1H-imidazole-4,5-dicarboxy acid, and Himba = 4-(1H-imidazole-1-ly) benzoic acid), has been obtained by the hydrothermal reaction. Single crystal X-ray diffraction analysis shows that complex 1 exhibits one-dimensional (1-D) ribbon-double chain composed of tetranuclear europium clusters, and these chains are further linked by Himba ligands into the 2-D corrugated layer arrays. Complex 1 exhibits efficiently sensitized red luminescence in visible region in N,N-dimethyl formamide (DMF) based on characterization emission of europium(III) ion. When Cd(NO3)2 is dropped in the DMF suspension of 1, the luminescence intensity increases linearly, rapidly, which indicates it may be employed as a fluorescent ratiometric probe for detection pollutant Cd(II) anion. In addition, complex 1 is characterized by elemental analysis, IR spectra, thermogravimetric (TG) analysis and PXRD measurement.A unique europium coordination polymer based on mixed carboxylic acid ligands, {[Eu4(Pimda)4 (Imiba)2·4H2O]·4H2O}n has been synthesized and characterized, 1 may be employed as a fluorescent ratiometric probe for pollutant Cd(II) ion.

•Two isostructural 3D metal–organic frameworks have been synthesized under hydrothermal conditions.•Each polymer possesses similar infinite rod-shaped chain consist of dinuclear europium-carboxylate building units•The chains are pillared by dicarboxylate ligands to give rise to 3D frameworks featuring a (6, 4)-connected pcu topology.•It also demonstrates tunable or switchable fluorescence signals in response to the different solvents.•Polymer1 may be employed as a fluorescence ratiometric probe for pollutant cations.Two isostructural 3D europium metal–organic frameworks incorporating similar Eu-fluorine substituted carboxylate tectonics, {[Eu4(Mimda)4 (Tfpa)2·4H2O]}n (1) and {[Eu4(Pimda)4 (Tfpa)2·4H2O]}n (2) (Mimda = 2-methyl-1H-imidazole - 4, 5–dicarboxy acid, while Pimda = 2-propyl-1H-imidazole - 4, 5–dicarboxy acid and Tfpa = (3,4,5,6-tetrafluoro-1,2 phthalate acid) have been synthesized under the hydrothermal conditions. They have been systematically characterized by elemental analyses, IR spectra and PXRD patterns. Single crystal X-ray diffraction analysis reveals that each polymer possesses infinite rod-shaped chain consist of dinuclear Eu-carboxylate building units, which are further pillared by imidazole-dicarboxylate ligands to give rise to 3D open non-interpenetrated frameworks, featuring a (6, 4)-connected pseudo-primitive cubic (pcu) topology. Both two polymers exhibit efficiently sensitized red luminescence due to an energy transfer from substituted dicarboxylate ligand to Eu(III) ions in solid state. Polymer 1 also demonstrates tunable or switchable fluorescence signals in response to the different solvents. Moreover, the luminescent intensity of 1 is increased linearly with the increasing concentration of Pb2 + cation in N,N-dimethyl formamide (DMF) suspension, while shows declining trend with Cd2 + cation being introduced.Two isostructural 3D europium metal–organic frameworks incorporating similar Eu-fluorine substituted carboxylate moieties have been synthesized under hydrothermal conditions. Each polymer possesses the open 3D non-interpenetrated frameworks featuring a (6, 4)-connected pseudo-primitive cubic (pcu) topology. It also demonstrates tunable or switchable fluorescence signals in response to the different solvates. The luminescent intensity of 1 is increased linear with the increasing concentration of Pb2 + cation in N,N-dimethyl formamide (DMF) suspension, and polymer 1 may be employed as a fluorescence ratiometric probe for pollutant cations.

•Two 3-D Co(II) coordination polymers incorporating similar substituted imidazole- dicarboxylate have been afforded.•They are nearly isostructural, possessing similar units based on trinuclear clusters.•The dipyridyl-type ancillary ligand does not result in obvious diversity structures.•Magnetic measurements revealed spin-canting-like antiferromagnetism behaviors for compounds at lower temperature.Two three dimensional (3D) Co(II) coordination polymers incorporating similar substituted imidazole-dicarboxylate and dipyridyl-type ancillary ligands pillared layer, namely, {Co3(mimda3 −)2 (bpe)3·3H2O}n (1) and {Co3 (eimda3 −)2(bipy)3·8H2O}n (2) (H3mimda = 1H-2-methyl-4,5-imidazole-dicarboxylic acid, while H3eimda = 1H-2-ethyl-4,5-imidazole-dicarboxylic acid, bpe = 1,2-di(4-pyridyl) ethylene and bipy = 4, 4′-bipyridine) have been successfully synthesized. Both polymers 1 and 2 have been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, and thermogravimetric analysis (TGA). X-ray structural analysis reveals that they are nearly isostructural, possessing similar symmetry units based on trinuclear clusters, and further is propagated into a Kagomé-like lattice. The lattice consists of corner-sharing triangles of spins with magnetic coupling between the nearest neighboring Co(II) ions. Magnetic measurements revealed spin-canting-like antiferromagnetism behaviors for compounds 1 and 2 at lower temperature. The interaction in 1 is slightly stronger than that of 2, which can be explained by the discrepancy of organic linker between the adjacent Co(II) centers.Two three dimensional (3D) Co(II) coordination polymers incorporating similar substituted imidazole-dicarboxylate and dipyridyl-type ancillary ligands pillared layer have been successfully afforded. X-ray structural analysis reveals that they are nearly isostructural and magnetic measurements revealed spin-canting-like antiferromagnetism behaviors at lower temperature.We show a mixed ligands approach used in a promising way to construct new molecular magnetic materials.

•A luminescent 2D layered Eu-MOF was designed and synthesized by the hydrothermal method.•TGA and PXRD show that the complex demonstrates excellent thermal stability.•The Eu-MOF shows selectively and sensitively fluorescence quenched or enhanced by some small organic molecule solvents.•Eu-MOF luminescence emission could be quantitatively quenched upon the addition of phenylamine.A luminescent europium metal-organic framework[Eu(Hbptc)(H2O)3]n (1) has been successfully prepared by the facile hydrothermal reaction of Eu(NO3)3 ⋅ 6H2O and the π-conjugated ligand H4bptc (H4bptc = biphenyl-2,3,3′,5′-tetracarboxylic acid). Single crystal structure analysis reveals that 1 exhibits a 2D layered structure. The luminescence studies revealed that this material can be selectively and sensitively quenched or enhanced by some small organic molecule solvents, showing potential as fluorescence probe.A highly luminescent 2D Eu-MOF was designed and successfully synthesized. Eu-MOF can sense some organic small molecules based on luminescence quenching effect. Interestingly, the visible red emission of Eu-MOF could be quantitatively quenched upon the addition of phenylamine at low concentrations.

Reaction between silver salt and conjugational N-hetrocyclic carboxylic acid with the presence of bipyridyl skeletons auxiliary ligand afforded a d10 metal polymer namely [(ddpp)Ag(bipy) (1)] (ddpp = 2, 5-di(2′,4′-dicarboxylphenyl)pyridine, bipy = 4,4′-bipyridine). It was characterized by elements analysis, infrared spectroscopy, single crystal X-ray diffraction and thermogravimetry studying. For the polymer 1, silver centers are three coordinated geometry with an ON2 donor set provided by ddpp and bipy. The polymer 1 is built from 1-D alternative/zig-zag chain, as the secondary building unit, and further stacks via hydrogen bonds which formed between two isophthalic moieties of ddpp ligands and weak interactions to generate a two-dimensional, 2D supramolecular layer. Moreover, the polymer 1 displays thermal stability in solid state and the luminescence behaviour is also investigated in a dimethyl sulphoxide solution at ambient temperature, and it also can be applied in design of sensors to detect of trace aluminum, zinc and calcium ion.

A family of heteronuclear metal organic frameworks (MOFs) using lanthanide and transition metal ion based on a rigid ligand of substituted imidazoledicarboxylic acid, namely, {[Ln2Zn2 (μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·mn H2O}, Ln = Nd, m = 2 (1), Ln = Ho, m = 3 (2), Ln = Er, m = 2 (3), Ln = Yb, m = 3 (4), [Tb2Co2(μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·2nH2O} (5) and [Dy2Co2 (μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·nH2O} (6), (H3mimda = 1H-2-methyl-4,5-imidazole-dicarboxylic acid), have been developed and characterized. All the complexes (except for a little disparity for 1) are isostructural, and all crystallize in the monoclinic system. They possess an extended reticular-like porous structure constructed from corrugated 2D layers. Direct current (dc) magnetic susceptibility measurements for 1–5 indicated depopulation of the Stark components at low temperature and/or possible weak anti-ferromagnetic interactions within hetero-nuclear MOFs. Alternating current (ac) susceptibility studies reveal that the Dy(III)–Co(II) complex exhibits both possible ferromagnetic couplings and frequency-dependent out-of-phase signals, behaviour of single-ion magnet nature. Fluorescence properties of series complexes both in near-infrared (NIR) and visible regions have been comparatively studied.

A family of six new homo-lanthanide coordination polymers incorporating a conjugated ligand of 2,5-di(2′,4′-dicarboxylpheny)pyridine, namely, {[Ce(μ3−ddpp)]·4H2O}n (1), {[Nd(μ3−ddpp)]·2H2O}n (2), {[Sm(μ6−ddpp)]·H2O}·H2O}n (3), {[Eu(μ6−ddpp)]·H2O}n (4), {[Tb(μ6−ddpp)]·H2O}n (5), and {[Er(μ6−ddpp)]·H2O}n (6) (H3ddpp = 2,5-di(2′,4′-dicarboxylpheny)pyridine acid), has been prepared successfully through solvothermal reactions. Polymers 1–6 exhibit various coordination environments and different multi-dimensions, but they are all assembled in a one dimensional (1-D) Ln–carboxylate chain. Polymer 1 only shows a 1-D ribbon chain, while polymer 2 exhibits a binodal (3, 8)-connected topology net. Heavy lanthanide polymers 4–6 possess 3D frameworks based on a rare (4, 8)-connected msw framework. Thermogravimetric and different thermal analysis measurements indicate that they all display high thermal stability. The luminescence emission spectra display characteristic f–f transition emissions of Ln(III) polymers in visible or near infrared (NIR) regions. The fluorescent ligand H2ddpp provides efficient energy transfer for the sensitization of Eu(III) and Tb(III) ions in the visible region, among which a Tb(III) polymer may be employed as a fluorescence ratiometric probe for the pollutant CrO42− anion.

The reactions in mixtures of lanthanide oxides and biphenyl-2,3,3′,5′-tetracarboxylic acid, in the presence of aqueous solution, result in two interesting lanthanide–organic coordination polymers, formulated as{[Eu(Hbptc)(H2O)4]·H2O}n (1) and [Sm(Hbptc)(H2O)3]}n (2), (H4bptc = biphenyl-2,3,3′,5′-tetracarboxylic acid). The polymers 1 and 2 are built from 2D corrugated layer. The 2D layers are further interconnected to form the 3D framework by hydrogen bonds between water molecules and carboxyl groups. Both the complexes 1 and 2 exhibit efficient sensitized luminescence in the visible region in the solid state based on characterization emission of europium(III) and samarium(III) ions, respectively.Two new 2D lanthanide–organic frameworks assembled by the asymmetric biphenyl-tetracarboxylic acid ligand have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. They display strong characteristic fluorescence from the f–f transitions of lanthanide ion, as well as high thermal stability.

A heteronuclear metal organic framework containing erbium(III) and cobalt(II) ion based on a rigid ligand of substituted imidazoledicarboxylic acid has been synthesized and characterized by single-crystal X-ray diffraction analysis (CIF file CCDC no. 1019455). It’s formula is [Er2Co2(μ3-HMimda)2(μ3-Mimda)2 · 4H2O]n · 2nH2O, (H3Mimda = 1-H-2-methyl-4,5-imidazole-dicarboxylic acid). The complex crystallizes in the monoclinic system. It possesses an extended grid-like porous structure constructed from corrugated shaped 2D layer. Direct current magnetic susceptibility measurements for indicated the depopulation of the Stark components at low temperature and possible very weak antiferromagnetic interactions within heteronuclear MOF.

A novel binuclear iron(III) Schiff base complex [Fe2(NO2-Salpn)2(μ-OH)2] · H2O (I) (NO2-Salpn = 5-nitrosalicylaldehyde-1,3-propanediamine) has been obtained through one-pot refluxing and condensation. Complex I was established by single-crystal X-ray diffraction analysis (CIF file CCDC no. 1005239) and further characterized by elemental analysis, IR spectroscopy, electrochemical and magnetochemical measurements. Complex I consists of two pseudooctahedral high-spin iron(III) units doubly bridged by two hydroxyl groups. The inter hydrogen bonding interactions connect the adjacent binuclear units into one dimensional (1D) infinite chain, and these 1D chains are further propagated into the two dimensional (2D) supramolecular network by weak intermolecular interactions. Variable temperature magnetic measurements indicate the presence of strong antiferromagnetic interactions between the two adjacent iron(III) ions.

The solvothermal reaction of lanthanide nitrate and H4Diida ligand (H4Diida = 2-(4,5-dicarboxy-1H-imidazol-2-yl)-1H-imidazole-4,5-dicarboxylic acid) in the presence of ammonium oxalate results in a new three-dimensional (3D) lanthanide-organic framework, namely, {[Pr(Ida)(μ2-C2O4)0.5(H2O)2] · H2O}n (H2Ida = 1H-imidazole-4,5-dicarboxylic acid). H4Diida ligand can be in situ into Ida2− ions under the conditions, as unequivocally proved by these similar situations occurred in other systems. Single crystal X-ray diffraction analysis reveals the formation of a novel wave-like structure. It crystallizes in the monoclinic system, space group of P21/c. The polymer is built from two kinds of parallel alternately 1D infinite chain through the carboxylate double-linking adjacent Pr3+ cations, forming an extended 2D bilayer-like structure along the yz plane. Moreover, the polymer further stacks via weak interactions to generate a 3D supramolecular framework. The photoluminescence and magnetic properties for the polymer were also investigated and discussed.

A new cadmium(II) complex [Cd(NO2-Salen)2] containing Schiff base ligand (NO2-Salen = N-mono-5-nitro-salicylideneamino ethanato) has been prepared through facile condensation reaction of sub-stituted salicylaldehyde with ethylene-diamine and has been structurally characterized by elemental analysis, IR spectra and X-ray diffraction. It is formulated as C18H20CdN6O6 crystallizes in the orthorhombic system, space group of Pccn. The ligand of 5-nitrosalicylaldehyde-ethylene-diamine exhibits unusual mono asymmetry tridentate mode. The Cd2+ ion has a coordination number of six and assumes a distorted octahedral geometry. It exhibits an offset π-π stacking interaction between the substituted benzene ligands of adjacent mononuclear complexes. The neutral monomeric units of [Cd(NO2-Salen)2] are linked into a one-dimensional (1D) array via the intermolecular hydrogen bonds and π-π stacking interactions. The complex exhibits strong emission in visible region with the maximum wavelength of 428 nm, which is tentatively assigned to the π → π* intraligand fluorescence.

A new lanthanide-organic framework incorporating both substituted isonicotinic acid and oxalate coligand has been fabricated successfully through solvo-thermal reaction, namely, {[Er(μ2-H2Minca)](μ2-C2O4 · 2H2O] · 2H2O}n (I) (H3Minca = 2-(hydroxyl)-6-methyl-isonicotinic acid, H2C2O4 = oxalate acid). Complex I exhibits two dimensional (2D) corrugated networks with a 63 topology, in which {LnO8} polyhedron units are alternately linked through carboxylate and oxalate oxygen atoms into the 2D sheet layer (CIF file CCDC no. 948026). Thermogravimetric and different thermal analysis measurements indicate that I displays high thermal stability. Complex I also shows characteristic f-f transition luminescence emission in NIR region.

A new propylenediamine-bridged diunclear complex formulated as [Fe2(Salpn)3] (I) (pn = 1,2-propylenediamine, H2Salpn = N,N′-bis(salicylaldehyde)propylenediamine Schiff base) has been prepared from the template synthesis by the reaction of 1,2-propylenediamine with salicylaldehyde in the presence of the iron(III) salt. The metal centers adopt a slightly distorted octahedral geometry, and the Salpn ligands act in both bridging and chelating modes to form a dinuclear complex with the six-membered chelate rings. The magnetic susceptibility investigation for I indicates the presence of very weak antiferromagnetic coupling between the Fe3+ cations through the propylenediamine bridge.

A new zinc(II) complex Zn(H3Pimda)2] · H2O (I), where H3Pimda = 2-Propyl-1H-imidazole-4, 5-dicarboxylic acid, has been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. It crystallizes in the triclinic system, space group P\(\bar 1\), with a = 8.397(3), b = 11.271(4), c = 12.312(5)Å, α = 70.432(5), β = 70.984(5), γ = 74.897(5)°, V = 1022.9(7) Å3, Mr = 475.71, Z = 2, ρc = 1.695 g/cm3, F(000) = 488, μ = 1.151 mm−1, R = 0.0659 and Rw =0.1525 for 3769 observed reflections. The hydrogen bonding derived from the coordinated waters connects the mononuclear zinc complex units into a one-dimensional chain, and these chains are further linked by intermolecular hydrogen bonds into a 2D supramolecular network. Complex I also displays strong photoluminescence properties in the liquid state at room temperature.

A novel complex [K(NCS)3] · [Ni(N2C2H8)3] has been synthesized and characterized by X-ray diffraction. It crystalizes in trigonal system, and space group is P-3c1 with parameters: a = b = 11.6131(4) Å, c = 16.832(11) Å, γ = 120°, and Z = 4. The configuration of crystal consists of one [K(NCS)3]2− ion and one [Ni(en)3]2+ cation. The potassium ion is located in the symmetry center and octahedrally coordinated by six nitrogen atoms, the adjacent potassium ions were connected into an infinite one-dimensional chain structure via the isothiocyanato group bridge ligand. There are significant weak intermolecular hydrogen bond intractions between the sulphur atom of the isothiocyanato group and the nitrogen atom of [Ni(en)3] moiety, and the complex can be viewed as an unusual corner-sharing one-dimensional extended polymer.

A new ternary mixed-ligand complex [Cu2(sal-glu)2(bipy)(H2O)2] · (H2O) (bipy = 4,4′-bipyridine and sal-glu = salicylaldehyde l-glutamic Schiff base) has been synthesized and characterized by X-ray diffraction. It crystallizes in the triclinic system, space group P-1 with a = 9.6199(13) Å, b = 9.9111(13) Å, c = 9.9167(13) Å. The amino acid Schiff base coordinates to the Cu(II) ion in a tridentate mode including phenol-hydroxyl oxygen, carboxyl oxygen and amide nitrogen atom, while the bipy coordinates in bidentate bridging mode linking two Cu(II) ions. The [Cu2(sal-glu)2(bipy)(H2O)2] units are linked into 1-D chain structure and the bipy molecules are interspersed into parallel sheets via intermolecular hydrogen bonds. The carboxyl oxygen atoms, phenolic oxygen atoms and water oxygen atoms are involved in the extensive intermolecular hydrogen bond network between the water molecules and phenol-hydroxyl oxygen atoms from salicylaldehyde derived ligand.

A family of heteronuclear metal organic frameworks (MOFs) using lanthanide and transition metal ion based on a rigid ligand of substituted imidazoledicarboxylic acid, namely, {[Ln2Zn2 (μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·mn H2O}, Ln = Nd, m = 2 (1), Ln = Ho, m = 3 (2), Ln = Er, m = 2 (3), Ln = Yb, m = 3 (4), [Tb2Co2(μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·2nH2O} (5) and [Dy2Co2 (μ3-Hmimda)2 (μ3-mimda)2·4H2O]n·nH2O} (6), (H3mimda = 1H-2-methyl-4,5-imidazole-dicarboxylic acid), have been developed and characterized. All the complexes (except for a little disparity for 1) are isostructural, and all crystallize in the monoclinic system. They possess an extended reticular-like porous structure constructed from corrugated 2D layers. Direct current (dc) magnetic susceptibility measurements for 1–5 indicated depopulation of the Stark components at low temperature and/or possible weak anti-ferromagnetic interactions within hetero-nuclear MOFs. Alternating current (ac) susceptibility studies reveal that the Dy(III)–Co(II) complex exhibits both possible ferromagnetic couplings and frequency-dependent out-of-phase signals, behaviour of single-ion magnet nature. Fluorescence properties of series complexes both in near-infrared (NIR) and visible regions have been comparatively studied.